package 牛客_面试必刷.Month07.day11;

import java.util.Stack;

public class 用两个栈实现队列 {
    Stack<Integer> stack1 = new Stack<Integer>();
    Stack<Integer> stack2 = new Stack<Integer>();

    public void push(int node) {
        stack1.add(node);
    }

    public int pop() {
        if(stack2.isEmpty()){
            if(stack1.isEmpty()){
                throw new RuntimeException("Queue is empty!!!");
            }else{
                while(!stack1.isEmpty()){
                    stack2.push(stack1.pop());
                }
            }
        }
        return stack2.pop();
    }
}
